// 设置画布

const canvas = document.querySelector('canvas');
// HTMLCanvasElement.getContext() 方法返回 canvas 上下文
const ctx = canvas.getContext('2d');
const p = document.querySelector('p');

const width = canvas.width = window.innerWidth;
const height = canvas.height = window.innerHeight;

// 生成随机数的函数

function random(min, max) {
  const num = Math.floor(Math.random() * (max - min)) + min;
  return num;
}

// 生成随机颜色值的函数

function randomColor() {
  const color = 'rgb(' +
    random(0, 255) + ',' +
    random(0, 255) + ',' +
    random(0, 255) + ')';
  return color;
}

// 定义 Ball 构造器
// function Ball(x, y, velX, velY, color, size) {
//   this.x = x;
//   this.y = y;
//   this.velX = velX;
//   this.velY = velY;
//   this.color = color;
//   this.size = size;
// }

// Shape 构造函数
function Shape(x, y, velX, velY, exists) {
  this.x = x;
  this.y = y;
  this.velX = velX;
  this.velY = velY;
  this.exists = exists;
}

// 重写 Ball 构造函数
function Ball(x, y, velX, velY, color, size, exists) {
  // 继承Shape，组合继承
  Shape.call(this, x, y, velX, velY, exists);
  this.color = color;
  this.size = size;
}

// EvilCircle 构造函数
function EvilCircle(x, y, velX, velY, color, size, exists) {
  Shape.call(this, x, y, velX, velY, exists);
  this.color = color;
  this.size = size;
}

// 定义彩球绘制函数
// CanvasRenderContext2D.beginPath() 通过清空子路径列表开始一个新路径的方法（开始绘制）
// context.arc(x, y, r, sAngle, eAngle) 画圆， r 半径，sAngle 起始角， eAngle 结束角
// context.fill() 以填充的方式绘制图像
// context.stroke() 以线条方式绘制图像
Ball.prototype.draw = function () {
  ctx.beginPath();
  ctx.fillStyle = this.color;
  ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
  ctx.fill();
};

// 恶魔圈绘制函数
EvilCircle.prototype.draw = function () {
  ctx.beginPath();
  ctx.lineWidth = 3;
  ctx.strokeStyle = this.color;
  ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
  ctx.stroke();
};

// 定义彩球更新函数
Ball.prototype.update = function () {
  if ((this.x + this.size) >= width) {
    this.velX = -(this.velX);
  }

  if ((this.x - this.size) <= 0) {
    this.velX = -(this.velX);
  }

  if ((this.y + this.size) >= height) {
    this.velY = -(this.velY);
  }

  if ((this.y - this.size) <= 0) {
    this.velY = -(this.velY);
  }

  this.x += this.velX;
  this.y += this.velY;
};

// 恶魔圈位置监测函数
EvilCircle.prototype.checkBounds = function () {
  if ((this.x + this.size) >= width) {
    this.x -= this.size;
  }

  if ((this.x - this.size) <= 0) {
    this.x += this.size;
  }

  if ((this.y + this.size) >= height) {
    this.y -= this.size;
  }

  if ((this.y - this.size) <= 0) {
    this.y += this.size;
  }
};

// 恶魔圈移动函数
EvilCircle.prototype.setControls = function () {
  window.onkeydown = (e) => {
    if (e.key === 'a') {
      this.x -= this.velX;
    } else if (e.key === 'd') {
      this.x += this.velX;
    } else if (e.key === 'w') {
      this.y -= this.velY;
    } else if (e.key === 's') {
      this.y += this.velY;
    }
  }
};

// 定义碰撞检测函数

Ball.prototype.collisionDetect = function () {
  for (let j = 0; j < balls.length; j++) {
    if (this !== balls[j] && balls[j].exists) {
      const dx = this.x - balls[j].x;
      const dy = this.y - balls[j].y;
      const distance = Math.sqrt(dx * dx + dy * dy);

      if (distance < this.size + balls[j].size) {
        balls[j].color = this.color = randomColor();
      }
    }
  }
};

// 恶魔圈碰撞监测
EvilCircle.prototype.collisionDetect = function () {
  for (let j = 0; j < balls.length; j++) {
    if (balls[j].exists) {
      const dx = this.x - balls[j].x;
      const dy = this.y - balls[j].y;
      const distance = Math.sqrt(dx * dx + dy * dy);

      if (distance < this.size + balls[j].size) {
        balls[j].exists = false;
        // balls.length--;
        ballCount--;
        p.innerText = `还剩${ballCount}个球`
      }
    }
  }
};

// 定义一个数组，生成并保存所有的球

let balls = [];
let ballCount = 25;

while (balls.length < ballCount) {
  const size = random(10, 20);
  let ball = new Ball(
    // 为避免绘制错误，球至少离画布边缘球本身一倍宽度的距离
    random(0 + size, width - size),
    random(0 + size, height - size),
    random(-7, 7),
    random(-7, 7),
    randomColor(),
    size,
    true
  );
  balls.push(ball);
}

// 创建恶魔圈
let size = 10;
let evilCircle = new EvilCircle(
  random(0 + size, width - size),
  random(0 + size, height - size),
  10,
  10,
  'white',
  size,
  true
)
// 恶魔圈移动
evilCircle.setControls();

// 定义一个循环来不停地播放

function loop() {
  ctx.fillStyle = 'rgba(0,0,0,0.25)';
  ctx.fillRect(0, 0, width, height);

  evilCircle.draw();
  evilCircle.checkBounds();
  evilCircle.collisionDetect();

  for (let i = 0; i < balls.length; i++) {
    if (balls[i].exists) {
      balls[i].draw();
      balls[i].update();
      balls[i].collisionDetect();
    }
  }

  requestAnimationFrame(loop);
}

loop();